Basal cell adenoma in the parotid gland: CT and MR findings

Basal cell adenoma is a rare benign salivary gland epithelial tumor, usually involving the parotid gland. We report CT and MR findings of three cases with basal cell adenoma occurring in the parotid gland. The three cases presented here demonstrate a well-circumscribed tumor, which showed a cystic and solid, or the pure solid mass. They were well enhanced after contrast matter injection. The solid portion of the mass was isoattenuated at CT, with intermediate signal intensity on T1- and T2-weighted MR images. Its cystic portion was hyperintense on both T1- and T2-weighted MR images. It had a hypointense rim on T2-weighted image.     

A case of liver echinococcosis mimicing a solid liver tumor.

A case of hepatic echinococcosis mimicing a solid tumor was presented. The echinococcosis appeared as an echogenic mass in US, a low density area in CT, and an area of low (T1-weighted image) and high (T2-weighted image) intensity in MRI. Echo-guided biopsy showed PAS-positive cuticle layer of echinococcus in the necrotic tissue. Anular features around the lesion noted in MRI seemed to imply increased hepatic tissue water (congestion and/or edema). When a solid tumor is noted in the liver, proper history taking and awareness of this disease will decrease the chance of misdiagnosis.     

颈部囊性病变的多排螺旋CT和MRI影像学特征分析

目的：分析颈部囊性病变的多排螺旋CT和MRI影像学特征。方法回顾性分析41例经病理证实的颈部囊性病变的解剖部位及多排螺旋CT和MRI影像学征象。结果颈部囊性病变多形状规则,边界清晰。20例甲状舌管囊肿位于正中线舌骨水平或略偏,与甲状软骨关系密切,MRI征象为长 T1长 T2信号,信号均匀,增强扫描囊壁轻度强化;11例第二腮裂囊肿位多于胸锁乳突肌前内侧,MRI为囊性长T1长T2信号,信号均匀,囊肿内CT值为水样密度,增强扫描囊壁轻度强化;2例表皮样囊肿位于颈中线舌骨水平、颈后部,CT扫描密度均匀,增强未见明显强化;4例会厌囊肿位于会厌前间隙内,MRI影像为囊性长T1长T2信号肿块,信号均匀,CT影像为囊性薄壁低密度肿块,密度均匀;4例淋巴管瘤主要位于颈后三角区,MRI肿块呈等T1长T2信号,内部可见分隔,囊腔大小不等,增强扫描其分隔可见强化。结论颈部不同囊性病变的解剖位置和影像学征象有一定的特点,经过综合分析,可以做出正确诊断。     

Pleomorphic Adenoma Mimicking Malignant Tumor in the Parapharyngeal Space in a Patient with Gastric Carcinoma

A 68-year-old man underwent total gastrectomy for stomach cancer. On the follow-up FDG PET/CT image 18 months later, intense focal ¹⁸F-fluorodeoxyglucose (FDG) uptake was noted in the right parapharyngeal space. This lesion showed intermediate signal intensity on T1-weighted image and heterogeneous high signal intensity on T2-weighted image. The mass was heterogenously enhanced by gadolinium enhancement. This lesion was pathologically confirmed as pleomorphic adenoma by excision. This case highlights the fact that both benign and malignant lesions in the parotid gland may exhibit intense FDG activity and the need for pathologic confirmation of parotid gland lesions for accurate disease staging.     

MR imaging in the assessment of lung cancer patients: primary lung cancer staging, evaluation of therapeutic effect and diagnosis of recurrent tumor

Magnetic resonance imaging and computed tomography were compared in a prospective study of 137 lung cancer patients proved by surgery or autopsy for determining the staging, evaluation of therapeutic effect and diagnosis of recurrent tumor. 1. Lung cancer staging In peripheral lung cancer, T1 and T2 relaxation times of the tumors before operation have some correlation with those of operated specimens. These relaxation times, however, are of limited nodule characterization. Hilar mass and adjacent pulmonary consolidation (obstructive pneumonia or collapse) can be distinguished on T2-weighted image (77%) and Gd-DTPA enhanced image (80%). Therefore these images help in distinguishing tumor from peripheral lung disease. In the diagnosis of tumor invasion to the heart and great vessels, MRI is superior to CT because MRI can be helpful in distinguishing true mass from heart and great vessels. As for the chest wall, MRI is more useful than CT in detecting tumor invasion especially to the thoracic inlet and superior regions. In the diagnosis of mediastinal and hilar lymphadenopathy, MRI is equivalent or slightly inferior to CT, but MRI can easily demonstrate the lymphadenopathy at subcarinal region on coronal image. 2. Evaluation of therapeutic effect in lung cancer patients treated by radiation and chemotherapy MRI patterns of therapeutic effect was divided into 3 types. It is suggested that there is some correlation between these patterns and histologic types. MRI can easily demonstrate necrotic area on T2-weighted and Gd-DTPA enhanced images. 3. Diagnosis of recurrent tumor in treated lung cancer Concerning detecting recurrent tumor after surgery or irradiation, and delineating tumor from radiation pneumonitis, T2-weighted and Gd-DTPA enhanced images are of clinical value.     

Ectopic cervical thymus in an infant

We report a case of accessory cervical thymus presenting as a unilateral neck mass in a 2-month-old boy. Ultrasonography (US) showed a mass isoechogenic to muscle in the left neck. Computed tomography (CT) revealed a well-defined, mildly enhanced mass located anterior to the sternocleidomastoid muscle, anterolateral to the carotid sheath, and posterior to the submandibular gland. On magnetic resonance imaging (MRI), the mass was isointense to muscle on T1-weighted images and hyperintense to muscle on T2-weighted images. Diffusion-weighted images showed relatively low apparent diffusion coefficient (ADC) values, and the mass was slightly enhanced after administration of contrast material. We suspected ectopic thymus, but we could not exclude the possibility of a malignant lesion. Therefore, the tumor was surgically resected. The histological diagnosis was ectopic cervical thymus. Ectopic thymus should be included in the differential diagnosis of a submandibular or cervical mass in infants. US and MRI can provide useful information for the diagnosis of ectopic cervical thymus.     

Hepatic hemangioma presenting atypical radiologic findings: a case report

A 69-year-old woman was referred to our hospital due to a liver tumor that was incidentally noted on ultrasound (US). US revealed a pedunculated mass of 5 cm in diameter, with a heterogeneous echo pattern. On arterial phase dynamic contrast-enhanced computed tomography (CT), a tiny enhancing dot in the upper aspect of the mass was seen; whereas, the main portion of the lesion appeared as hypoattenuating. The tumor was of low intensity on T1-weighted magnetic resonance (MR) images, and showed slightly heterogeneous high intensity on T2-weighted MR images. The most characteristic feature of the tumor was its exophytic appearance. On post-gadolinium hepatic arterial dominant-phase MR images, the tumor showed nodular enhancement centrally, with progressive spread of enhancement on later images. Angiography showed dilatation of the right posterior inferior branch of the hepatic artery and C-shaped opacification. Since we could not rule out malignancy for these nonspecific radiologic findings, a partial resection of the liver was carried out, resulting in a pathological diagnosis of hepatic hemangioma. This hemangioma had marked hyalinization and fibrosis, causing a heterogeneous appearance on MR images. The tumor presented an exophytic appearance, which caused some diagnostic confusion.     

CT, MR, and Angiography Findings of a Solitary Fibrous Tumor of the Larynx: a Case Report

This report details the CT, MR, and angiography findings of a solitary fibrous tumor involving the larynx of a 34-year-old man. A precontrast CT scan revealed a well-defined isodense mass in the submucosal region of the supraglottic larynx. The tumor appeared as a mixed intensity lesion on the T1- and T2-weighted MR images. A T2-weighted MR image showed a central, round, and low signal intensity area within the mass. For both the CT and MR images, the mass demonstrated heterogeneous enhancement following the administration of contrast material. The angiography showed a hypervascular tumor with heterogeneous persistent staining.     

Amebic liver abscess: MR imaging

Hepatic magnetic resonance (MR) imaging was performed in 12 patients with 13 amebic liver abscesses. While no specific image or intensity pattern was noted, most lesions were round or oval with smooth, well-defined margins; had decreased signal intensity compared with that of liver parenchyma on T1-weighted images and increased signal intensity on T2-weighted images; and had prominent, often multiple rims of variable signal intensity. Signal homogeneity within the abscess was present more often on T1- than on T2-weighted images. Diaphragmatic disruption was seen in two cases on coronal MR images. An amebic empyema was differentiable from sympathetic pleural effusions by its hyperintensity on both T1- and T2-weighted images. In patients who also underwent computed tomography (CT) or ultrasonography (US), no lesion was missed with any modality, and except for shape, no consistent features were found among images obtained with the different modalities. The data suggest that CT, US, and MR imaging are comparably effective in the detection of amebic abscess.     

Germ cell tumors of the central nervous system originating from non-pineal regions: CT and MR features.

CT and MR findings were retrospectively reviewed in 12 patients with germ cell tumors originating from the non-pineal regions. Cystic or necrotic components were seen in 6 patients. Of 4 germinomas, 2 showed mixed density on the CT. The MR signal intensity of the tumor was non-specific. Of 8 germinomas, 4 were inhomogeneously enhanced on postcontrast CT and T1-weighted MR images. CT and MR features of germinomas originating from non-pineal regions frequently differ from those of germinomas originating from the pineal region. The mass of the tumor often appeared cystic and inhomogeneously enhanced following contrast infusion.     

Metastatic liver tumor from cystic ovarian carcinomas: CT and MRI appearance.

OBJECTIVE: The initial and follow-up CT and MRI images of ten patients with hepatic metastases from ovarian tumors were retrospectively analyzed to establish their features and sequential changes in appearance. MATERIALS AND METHODS: Ten patients with hepatic metastasis from ovarian tumors received initial and follow-up CT and MRI examinations. Six patients were followed up every two to three weeks before surgical tumor resection. Both CT and MR images were analyzed by two radiologists. RESULTS: A total of fourteen lesions were detected by CT and MRI in 10 patients. All 14 lesions were demonstrated as areas of marked hyperintensity on T2-weighted MRI. Eleven cyst-like tumors were demonstrated as round or oval low density lesions on CT and as areas of hypointensity on T1-weighted imaging. Three lesions were shown as solid masses with slightly low attenuation at the initial CT examination and slightly low or iso-intensity areas on T1-weighted imaging, and these lesions showed early peripheral globular enhancement and delayed enhancement on contrast-enhanced CT and MR imaging. Cystic formation was observed two to three weeks later after initial study in all the 3 solid lesions. Rapid subcapsular effusion, which showed obvious enhancement on delayed Gd-DTPA enhanced MR imaging, was observed in two patients. CONCLUSION: The hepatic metastatic tumor from cystic ovarian carcinoma may manifest as a well-defined cystic lesion or as a solid mass, and the solid mass shows delayed enhancement on contrast-enhanced CT and MR imaging. Furthermore, rapid cystic formation and rapid subcapsular extension is frequently seen.     

Odontogenic myxoma of maxillary sinus: CT and MR-pathologic correlation

We showed the characteristic features of odontogenic myxoma in the maxillary sinus with computed tomography (CT), magnetic resonance imaging (MRI), and histopathological findings. CT images showed a multilocular soft tissue mass with bone destruction and thinning, and the characteristic finding of this lesion as strands of fine lacelike density. MRI revealed intermediate signal intensity on T1-weighted image and high signal intensity on T2-weighted image. MRI showed the erosive extent of the lesion into the adjacent structures. In contrast T1-weighted image, the peripheral portion of the lesion with a relatively large quantity of collagen bundles was enhanced, while the central portion with only mucoid component was not. The CT and MRI appearances correlated well with the histologic features and therefore were considered to be a useful tool for diagnosis of myxoma.     

Gadolinium-DOTA enhanced MR imaging of adnexal tumors

We conducted a retrospective study to assess the potential of contrast enhanced magnetic resonance (MR) imaging in evaluating adnexal tumors. Sixty patients with a total of 77 pelvic lesions underwent MR imaging at 1.5 T and transabdominal ultrasound (US). Precontrast T1- and T2-weighted and Gd-DOTA enhanced T1-weighted MR images were obtained. Diagnoses were proved by surgery in 57 patients. Of the 77 lesions, 54 masses were of ovarian origin, including 12 malignant disorders. Ultrasound demonstrated the lesions in 92%, whereas the sensitivity of unenhanced T2-weighted and postcontrast MR images was 98 and 96%, respectively. Compared to the T2-weighted images, postcontrast MR imaging showed superior overall tumor delineation, assessment of intratumoral architecture, and definition of tumor origin. Contrast enhancement of tumors did not differ significantly between normal ovary and benign and malignant lesions. All modalities were unable to predict malignancy of complex lesions. Based on our study, US remains the screening modality of choice in the evaluation of adnexal tumors. Contrast enhanced MR imaging may be valuable for assessing complex lesions or when the origin of the mass cannot be determined by US. Using contrast enhanced T1-weighted images instead of T2-weighted images may lead to a significant reduction in acquisition time.     

Osteonecrosis Mimicking Bone Metastasis in Femoral Head on 18F-FDG PET/CT: A Case Report

A 77-year-old woman underwent chemotherapy, radiotherapy, and brachytherapy for cervical cancer 9 years ago. On a follow-up ¹⁸F-fluorodeoxyglucose (FDG) PET/CT image, focal FDG uptake was noted in a focal osteolytic lesion in the right femoral head. During magnetic resonance imaging, this lesion showed subchondral dark-signal-intensity rim on T1-weighted image and double line sign on T2-weighted image, suggestive of osteonecrosis. The lesion was pathologically confirmed as osteonecrosis after surgery. This case demonstrates that osteonecrosis of the femoral head may demonstrate focal FDG uptake mimicking bone metastasis.     

MR of benign chondroblastoma of the temporal bone.

A benign chondroblastoma of the temporal bone in an 8-year-old boy is reported. Head CT showed an expansile mass with calcifications in the center. The tumor appeared as a well-lobulated, hypointense intraosseous mass on T1-weighted brain MR; it was isointense to brain parenchyma on intermediate-weighted images and enhanced homogenously with gadolinium.     

肾上腺外节细胞神经瘤的CT和MRI特征

目的 探讨肾上腺外节细胞神经瘤的CT和MRI特征,提高对该病的认识.资料与方法 回顾性分析8例经病理证实的肾上腺外节细胞神经瘤的CT和MRI表现,并与组织病理学特征作对比.结果 8例肾上腺外节细胞神经瘤发生于脊柱和脊柱旁区,圆形2例,伴足突的不规则形6例;7例边界完全清楚,1例部分边界清楚;5例CT均表现为均匀低密度,3例增强扫描呈轻-中度强化,2例肿瘤内可见强化线条影.5例MRI T1WI表现为稍低、等信号,T2WI呈不均匀高、显著高信号,增强后呈中等度明显强化,3例肿瘤内可见典型“漩涡征”.肿瘤镜下表现具有特征性,为黏液基质背景下大量梭形细胞及散在的或巢状分布的神经节细胞.免疫组化:S100(+),NF(+),Syn(+),CgA(+).结论 肾上腺外节细胞神经瘤好发部位为脊柱及脊柱旁区,CT和MRI表现具有一定的特征性.     

Angiomyolipoma arising in the thigh

A 41-year-old man presented with an asymptomatic mass in the right medial thigh. Magnetic resonance imaging (MRI) revealed a well-demarcated, 10-cm mass in the right adductor muscles. The margins of the mass exhibited high signal intensity and the rest showed low or iso signal intensity on T1-weighted MR images. However, the high signal intensity was decreased on T2-weighted images with fat suppression. The central part of the tumor was of inhomogeneous high signal intensity on T2-weighted images; after Gd-DTPA injection it enhanced inhomogeneously on T1-weighted images with fat suppression. On dynamic computed tomography (CT) in the arterial phase, there were strongly enhancing spotty areas in the tumor. At surgery, a yellow-whitish tumor was resected and a pathological diagnosis of angiomyolipoma (AML) in the thigh was made. Received: 21 June 1999 Revision requested: 28 July 1999 Revision received: 13 December 1999 Accepted: 15 December 1999     

Low-grade fibromyxoid sarcoma of the small bowel mesentery: computed tomography and magnetic resonance imaging findings

Low-grade fibromyxoid sarcoma (LGFMS) is a rare tumor that commonly arises in the lower extremities but rarely in the mesentery. We report computed tomography (CT) and magnetic resonance imaging (MRI) findings of LGFMS of the small bowel mesentery. On CT, the mass was composed of two components. One component, on its right side, appeared to have isointense attenuation relative to muscle, whereas the other component, on its left side, appeared to have low attenuation. On MRI the mass on the right side showed hypointensity similar to muscle on both T1-and T2-weighted images as well as mostly slight enhancement on contrast-enhanced T1-weighted images. On the other hand, the mass on the left side showed relative hypointensity on T1-weighted images and hyperintensity on T2-weighted images as well as intense enhancement on contrast-enhanced T1-weighted images, suggesting that the tumor contained myxoid tissue. The myxoid area of LGFMS may have a tendency to reveal intense enhancement on contrast-enhanced images.     

CT and MR findings of basal cell adenoma of the parotid gland

We report a case of basal cell adenoma in the left parotid gland. A 34-year-old woman presented with a non-tender mass in the left parotid gland. She had first noted it 7- years previously, and it had been gradually increasing in size. The tumor was well-circumscribed with a smooth contour. On noncontrast-enhanced CT, the tumor showed homogeneous soft tissue attenuation. No cystic portion or calcification was seen. The tumor showed homogeneous moderate enhancement on contrast-enhanced CT. Capsule-like ring enhancement was demonstrated. On T1-weighted MR imaging, the tumor was homogeneously hypointense to the surrounding parotid tissue and isointense to muscle. On T2-weighted imaging the tumor was homogeneously hyperintense to muscle but slightly hypointense to the surrounding parotid tissue. On Gd-enhanced T1-weighted imaging, the tumor demonstrated homogeneous moderate enhancement. Capsule-like ring enhancement was also demonstrated. Salivary (technetium-99m-pertechnetate) scintigraphy did not show any uptake in the tumor.     

Traumatic adrenal hemorrhage: radiologic findings

Four patients with traumatic hemorrhage in the right adrenal gland were examined with computed tomography (CT) and ultrasound (US) (initial US studies in three patients; follow-up study at least 1 month after the trauma in all patients). CT showed an enlarged inhomogeneous gland of normal to increased attenuation. This finding was associated with stranding of the periadrenal fat and stranding of the subcutaneous fat of the right flank, which corresponded to the site of trauma. US showed an enlarged, hyperechoic mass with a bright central echo that became cystic on follow-up examinations. Magnetic resonance imaging, performed in one patient, showed an enlarged gland that was isointense with liver on T1-weighted images and had increased signal intensity on T2-weighted images. Stranding of the periadrenal and subcutaneous fat of the right flank was present on T2-weighted images and appeared as streaky areas of increased signal intensity.